The present invention relates to power semiconductor devices and more particularly to heterojunction power semiconductor devices.
III-nitride heterojunction power semiconductor devices are desirable for power applications due to their high breakdown capability, and low ON resistance. U.S. patent application Ser. No. 11/004,212, assigned to the assignee of the present application illustrates an example of a III-nitride power semiconductor device.
Referring to FIG. 2, a III-nitride power semiconductor device as shown in U.S. patent application Ser. No. 11/004,212 includes substrate 28, buffer layer 30 disposed on substrate 28, a heterojunction 32 disposed on buffer layer 30, a protective layer 34 disposed on heterojunction 32, a schottky electrode 20 in schottky contact with heterojunction 32, and an ohmic contact 22 ohmically connected to heterojunction 32. Preferably, schottky contact 20 and ohmic contact 22 both include a field plate 36.
Heterojunction 32 includes a resistive III-nitride semiconductor body (resistive body) 38 and a III-nitride semiconductor barrier body (barrier body) 40 both formed with an alloy of InAlGaN. Resistive body 38 and barrier body 40 are selected so that the junction between the two creates a highly conductive two dimensional gas (2DEG) 42 due to spontaneous polarization and the piezoelectric effect as is well known in the art.
One known material for forming resistive body 38 is undoped GaN, and a known material for forming barrier body 40 is AlGaN.